blob: c55e918177ec2d36df16c2ba815af4b58b6ca61d [file] [log] [blame]
 /* * Copyright (c) 2011 The WebRTC project authors. All Rights Reserved. * * Use of this source code is governed by a BSD-style license * that can be found in the LICENSE file in the root of the source * tree. An additional intellectual property rights grant can be found * in the file PATENTS. All contributing project authors may * be found in the AUTHORS file in the root of the source tree. */ /****************************************************************** iLBC Speech Coder ANSI-C Source Code WebRtcIlbcfix_GetLspPoly.c ******************************************************************/ #include "defines.h" /*----------------------------------------------------------------* * Construct the polynomials F1(z) and F2(z) from the LSP * (Computations are done in Q24) * * The expansion is performed using the following recursion: * * f[0] = 1; * tmp = -2.0 * lsp[0]; * f[1] = tmp; * for (i=2; i<=5; i++) { * b = -2.0 * lsp[2*i-2]; * f[i] = tmp*f[i-1] + 2.0*f[i-2]; * for (j=i; j>=2; j--) { * f[j] = f[j] + tmp*f[j-1] + f[j-2]; * } * f[i] = f[i] + tmp; * } *---------------------------------------------------------------*/ void WebRtcIlbcfix_GetLspPoly( WebRtc_Word16 *lsp, /* (i) LSP in Q15 */ WebRtc_Word32 *f) /* (o) polonymial in Q24 */ { WebRtc_Word32 tmpW32; int i, j; WebRtc_Word16 high, low; WebRtc_Word16 *lspPtr; WebRtc_Word32 *fPtr; lspPtr = lsp; fPtr = f; /* f[0] = 1.0 (Q24) */ (*fPtr) = (WebRtc_Word32)16777216; fPtr++; (*fPtr) = WEBRTC_SPL_MUL((*lspPtr), -1024); fPtr++; lspPtr+=2; for(i=2; i<=5; i++) { (*fPtr) = fPtr[-2]; for(j=i; j>1; j--) { /* Compute f[j] = f[j] + tmp*f[j-1] + f[j-2]; */ high = (WebRtc_Word16)WEBRTC_SPL_RSHIFT_W32(fPtr[-1], 16); low = (WebRtc_Word16)WEBRTC_SPL_RSHIFT_W32(fPtr[-1]-WEBRTC_SPL_LSHIFT_W32(((WebRtc_Word32)high),16), 1); tmpW32 = WEBRTC_SPL_LSHIFT_W32(WEBRTC_SPL_MUL_16_16(high, (*lspPtr)), 2) + WEBRTC_SPL_LSHIFT_W32(WEBRTC_SPL_MUL_16_16_RSFT(low, (*lspPtr), 15), 2); (*fPtr) += fPtr[-2]; (*fPtr) -= tmpW32; fPtr--; } (*fPtr) -= (WebRtc_Word32)WEBRTC_SPL_LSHIFT_W32((WebRtc_Word32)(*lspPtr), 10); fPtr+=i; lspPtr+=2; } return; }